Patent GB-639827-A (GB)
Title: Improvements in or relating to gaseous electric discharge tubes
Inventor: REEVES ALEC HARLEY
IPC: H01J17/48
Filed: 1946-07-25
Abstract: 639,827. Discharge apparatus. STANDARD TELEPHONES & CABLES, Ltd. July 25, 1946,-No. 22140. [Class 39 (i)] [Also in Groups XL (b) and XL (c)] A cold cathode gas-filled " sequence " electric discharge tube comprises electrodes defining an array of separate glow discharge gaps constructed and arranged so that successive voltage impulses of like amplitude and waveform applied across a plurality of the said gaps in common cause, due to the ionization coupling between adjacent gaps of said array, successive gaps to fire in turn, one but not more than one previously unfired gap being fired in response to each successive impulse. Fig. 6 shows two sequence discharge tubes 10 and 17 arranged in a pulse-recording circuit (see Group XL (c)). Tube 10 has an anode 11 in the form of a wire, strip, or plate, and a cathode array 12 with individual rod cathodes mounted on a bus-bar 13 to form a comb. All the array gaps are of equal length, a separate priming gap 14 being used to stabilize the minimum level of ionization in the tube and to provide a starting gap 15. In tube 17 an alternative form of cathode array comprises a serrated metallic strip 19 coated with alumina or a similar discharge inhibiting substance except at the tips of the saw teeth. Separate output cathodes 16 and 22 are provided. The gas filling of the tubes is chosen to give a short deionizing time, and may comprise, for example, 92 per cent neon, 7 per cent hydrogen, and 1 per cent argon, at a total pressure of 100 mm. of mercury. On the application of a train of positive pulses to terminal 28, the first pulse fires gap 15, which remains discharging under the influence of the maintaining voltage from battery 29 after the pulse has passed. By the time the second pulse arrives, the energy level at the next gap is that due to the sum of the ionization potentials from the priming discharge at gap 14, the discharge at gap 15, and the voltage from battery 29. The spacings between gaps are so arranged that either the ionization from gap 15 has not had time to be fully effective at the third and subsequent gaps, or these gaps must be sufficiently far removed for the ionization coupling-from gap 15 to be too small to prime them. Curves are given showing the reduction of striking voltage with distance from a priming discharge, together with the effects of pulse amplitude and pulse width. With suitable gap spacings, the second pulse will fire the gap adjacent to gap 15, the third pulse will fire the next gap, and so on until discharge occurs at cathode 16, whereupon the second tube 17 operates, thus allowing time for deionization in tube 10 without interruption of the pulse recording process. In a modified tube, which may be used in a pulse distributer circuit (see Group XL (b)), the anode array comprises a series of separate wires or rods connected together either inside or outside the tube, and the cathode array comprises an equal number of cathode rods connected to individual output circuits. The anode-cathode gaps are all of equal length except for a first shorter starting gap. The maintaining battery and priming discharge gap are omitted, so that the discharge at each gap is extinguished between successive pulses.' As an alternative to having the starting gap shorter than the others, it may have its cathode coated with'or formed from a material of lower work function, or a small D.C. bias may be applied. Fig. 7 shows a practical embodiment of an eight-point counting tube with separate cathodes 42 and anodes 43 which are mounted on an insulating member made of lavite or other suitable material and comprising a central rod 39 joining parallel circular discs 40 and 41. Specification 639,839 is referred to.